Heart patients using herbal remedies may be at heightened risk of dangerous drug interactions

The use of these products is especially concerning among elderly patients who typically have co-morbidities, take multiple medications and are already at greater risk of bleeding, according to authors.

"Many people have a false sense of security about these herbal products because they are seen as 'natural,'" Arshad Jahangir, M.D., Professor of Medicine and Consultant Cardiologist, Mayo Clinic Arizona, adding that more than 15 million Americans reportedly use herbal remedies or high-dose vitamins. "But 'natural' doesn't always mean they are safe. Every compound we consume has some effect on the body, which is, in essence, why people are taking these products to begin with."

In addition to their direct effects on body function, these herbs can interact with medications used to treat heart disease, either reducing their effectiveness or increasing their potency, which may lead to bleeding or a greater risk for serious cardiac arrhythmias.

"We can see the effect of some of these herb-drug interactions -- some of which can be life-threatening -- on tests for blood clotting, liver enzymes and, with some medications, on electrocardiogram," Dr. Jahangir said.

According to the report, a major concern is that patients do not readily disclose their use of herbal remedies, and healthcare providers may not routinely ask about such use. In addition, because these herbs are regarded as food products, they are not subject to the same scrutiny and regulation as traditional medications.

"If patients aren't satisfied with their care today, many will turn to herbs because they believe these compounds can help them manage chronic conditions or improve health and prevent future disease," said Dr. Jahangir. "In fact, patients are willing to spend nearly the same or more on out-of-pocket expenses for herbal remedies than traditional medical care."

Two nationwide surveys conducted in 1990 and 1997 found that the number of visits to complementary and alternative providers increased from 427 million to 629 million, whereas the number of visits to primary care physicians remained basically unchanged.

Some examples of herbs and their adverse effect on heart disease management include:

• St. John's wort, which is typically used to treat depression, anxiety and sleep disorders among other problems, reduces the effectiveness of medications contributing to recurrences of arrhythmia, high blood pressure or increase in blood cholesterol levels and risk for future heart problems.
• Ginkgo biloba, which is supposedly used to improve circulation or sharpen the mind, increases bleeding risk in those taking warfarin or aspirin.
• Garlic, which supposedly helps boost the immune system and is commonly used for its cholesterol and blood pressure lowering properties, can also increase the risk of bleeding among those taking warfarin.

In addition to highlighting commonly used herbs and potential interactions with cardiovascular medications, the present review also outlines steps for improving their safe use and reducing harm among patients with heart disease.

"These herbs have been used for centuries -- well before today's cardiovascular medications -- and while they may have beneficial effects these need to be studied scientifically to better define their usefulness and, more importantly, identify their potential for harm when taken with medications that have proven benefit for patients with cardiovascular diseases," said Dr. Jahangir. "Patients, physicians, pharmacists and other healthcare providers need to know about the potential harm these herbs can have."

In addition to greater public education about the risks of using herbal products, patients and clinicians need to actively discuss the use of over-the-counter medications, supplements and herbal products in addition to prescription medications.